Biodiversity, Aquatic Environment

Environmental

Penta-Ocean Construction Group, with creating a rich environment as one of our management philosophies, is engaged in activities for the conservation of biodiversity, creation of aquatic environments, and initiatives toward nature positivity. In the future, we plan to disclose information in accordance with TNFD recommendations.

Action Guidelines on Biodiversity

To conserve and enhance biodiversity while contributing to the sustainable development of society, Penta-Ocean Construction Group established the Action Guidelines on Biodiversity in August 2025 as the foundation of our environmentally responsible and sustainable construction business activities.

Please click here to view our Action Guidelines on Biodiversity

Promotional Structure

The Sustainability Promotion Committee, chaired by the President, CEO and Representative Director, formulates and promotes company-wide policies, strategies, and activity plans related to biodiversity.

Initiatives to Create and Maintain Aquatic Environments

Application of Calcia Soil Stabilization Technology in the Creation of Shallow Areas, etc.

Shallow areas and tidal flats serve as habitats for many organisms. To conserve biodiversity, we are working on blue infrastructure development of shallow areas and tidal flats using dredged soil, Calcia stabilized soil, and Calcia artificial stone (artificial stone made by mixing dredged soil, steelmaking slag, blast furnace slag powder, etc.).

Example of Shallow area creation using Calcia Stabilized Soil

Mixing dredged soil and calcia reforming material with a backhoe — Mixing dredged soil and calcia reforming material
with a backhoe

Environmental Preservation during Construction Work

To suppress the impact on biodiversity during construction work, it is important to plan appropriate environmental preservation measures and ensure their reliable implementation. During the Tamagawa Sky Bridge construction project, efforts have been made to restore the surrounding environment as closely as possible to its original condition prior to construction, such as reusing removed soil for tidal flat restoration, in order to minimize the impact on tidal flat organisms.

Tamagawa Sky Bridge
to the bridge's surrounding environment

Temporary placement of tidal flat topsoil

Formation of Blue Carbon Ecosystems and Creation of Seaweed Beds

CO₂ Fixation through Blue Carbon and Other Means

In shallow areas formed with Calcia shallow soil and other materials, the growth of seaweed and seagrass capture atmospheric CO₂ as blue carbon, contributing to measures against global warming while also realizing a rich marine environment through blue carbon ecosystems. We conducted surveys on the growth status of seaweed and evaluated the amount of CO₂ fixed as blue carbon in the shallow area created in Aboshi District, Himeji City, Hyogo Prefecture, and carried out registration and sales as J Blue Credit^®. Additionally, the results of catch surveys such as basket net fishing in shallow areas, revealed an increase in species such as rockfish and sea cucumbers.

Seaweed growth was determined through a survey — Seaweed growth was determined
through a survey

Catch survey performed using basket net fishing — Catch survey performed using
basket net fishing

Development of Materials for Seaweed Growth

For seaweed to grow in shallow areas, it is necessary to provide stones or concrete blocks that seaweeds can cling and flourish. By installing Calcia artificial stone, a low-carbon material compared to concrete, in shallow areas or by capturing CO₂ in Calcia artificial stone, it is possible to reduce CO₂ emissions during construction. We are also developing Calcia artificial stone that enables better attachment and growth of seaweed compared to concrete.
Currently, we are developing a real-time seaweed growth monitoring system by attaching transmitters to seaweed to check growth status.

Transplantation and Creation of Seaweed Beds and Coral

Creating seaweed beds and coral growth areas requires understanding suitable environmental conditions, selecting appropriate sites, and transplantation techniques. We have been working on the creation of eelgrass beds for some time, and are improving the accuracy of site selection through calculations using genetic algorithms. In addition, in canal areas of Tokyo Bay and elsewhere, we are conducting growth tests in tanks and transplantation experiments in actual sea areas targeting the seagrass Zostera japonica, which can be utilized for blue carbon.

Suitable locations are selected using software-based simulations

Biodiversity Conservation in Terrestrial Areas

Development of Green Infrastructure-related Technologies

At the Institute of Technology located in Nasushiobara City, Tochigi Prefecture, we have established a biotope and have made improvements to the growth environment for aquatic plants and made efforts to attract aquatic insects such as dragonflies. These activities are part of the ongoing development of green infrastructure-related technologies. Surveys of species habitat conditions have confirmed that the biotope functions effectively as a habitat for a wide variety of organisms.

Measures for Protecting Rare Species

In order to protect the environment during construction work, we implement measures including protecting rare species, improving their cultivation and living environments, and relocating flora and fauna. To date, we have carried out efforts to protect species such as the Tohoku salamander, Gifu butterfly, Thunbergia laurifolia, and the small white butterfly along with improving habitats for species including fireflies and the endangered bekko tombo (Libellula angelina).